Composition



Fatented den. 3, 1&3?

STATES Zfiiiiig PATENT caries COMPOSITION No Drawing.

Application March 23, 1937,

Serial No. 132,617

21 Claims.

This invention relates to compositions of mata ter containing sulfamic acid and certain of its salts. It relates more particularly to the flameproofing and softening of textile and cellulosic compositions.

This invention has as an object the provision of fire-retardants for non-volatile readily combustible organic materials, as a further object the provision of fire-retardants for textiles and cellulosic materials, and as a still further object the provision of combined softeners and fireretardants for such materials as paper and regenerated cellulose film.

The above and other objects appearing hereinafter are accomplished by the following invention wherein sulfamic acid or certain of its salts are incorporated, by the methods and in the amounts set forth more fully below, with nonvolatile combustible organic materials, especially cellulosic substances such as paper, textiles, and regenerated cellulose thread or film. The resulting compositions, in all of the large numbers of cases I have tested, have a definitely decreased tendency to propagate flame and in many instances the cellulosic or other material is rendered quite flame-proof. Ammonium sulfamate in particular has shown an especially strong fire-retardant action as compared to ordinary known fire-retardants and in addition does not contribute to the treated products certain undesirable properties resulting from use of many known fire-retardants.

A satisfactory method of carrying out the invention consists simply in wetting or impregnating the material to be treated with an aqueous solution of the sulfamic acid or salt thereof of suitable strength, and drying the same. Materials thus impregnated or covered show a decreased tendency to ignite and burn, and/or a decreased rate of burning. Many such products will not propagate a flame under conditions whereby untreated materials are readily destroyed by fire. In the case of paper, regenerated cellulose, textiles, and the like, the sulfamic acid or salt often has a softening or plasticizing as well as a fire-retarding efiect.

The more detailed practice of the invention is illustrated by the following examples, wherein parts given are by weight unless otherwise stated. There are of course many forms of the invention other than these specific embodiments.

Example I Cotton fabric weighing about 1.5 ounces per square yard was immersed in an aqueous solution containing 20% by weight of ammonium sulfamate. After the cloth was thoroughly wet with the solution it was passed between tightly fitting rubber rollers to remove excess solution and then dried. The fabric thus treated retained about 19% by weight of ammonium sulfamate based on the original weight of the cloth. The treated cloth showed no increased stiffness or harshness and no tendency to dust or crock. When the treated cloth was brought into contact with a flame it merely charred at the point of contact with the flame and did not ignite under any conditions nor did it show any tendency to propagate a. flame.

When a similar cloth was impregnated with approximately 3% to 10% by weight of ammonium sulfamate it would ignite, but would burn much more slowly than untreated cloth. Cloth impregnated with less than 3% ammonium sulfamate showed only a slight decrease in rate of burning. Under like conditions, similar cotton voile containing about 1015%, by weight of ammoniumsulfamate would not continue to burn when ignited and charred only at the point of direct contact with the flame. Likewise, samples of the same cotton voile cloth which had been impregnated with other salts of sulfamic acid, for example, the calcium, sodium, zinc, aluminum, methylamine, ethylenediamine salts, by the method given above, showed either no tendency to ignite and burn, or showed a decreased rate of burning compared with untreated cloth. The degree of flame-proofness, or the fire-retardant effect, in each case was dependent upon the sulfamate used and amount of sulfamate which had been impregnated into the cloth.

Example II burned when ignited.

When samples of the same cloth were similarly impregnated with salts of sulfamic acid other than the ammonium salt, for example, the trimethylamine, pyridine, zinc, aluminum, and

ethylenediamine (disulfamate) salts, the treated samples likewise showed a lower rate of combustion. Such treated samples contained from 11 to 13% of the sulfamate. The ammonium sulfamate and ethylenediamine disulfamate were more effective as fire-retardants than the trimethylamine salt and the pyridine salt, and, of the metal salts, the aluminum, sodium and calcium salts were more effective than the zinc salt.

Example I]! Textile fabrics, including a heavy cotton duck, cotton muslin, cotton flannel, wool, silk, and cellulose acetate rayon fabric, were treated with a 15% aqueous solution of ammonium sulfamate as described in Example II, and products showing a decreased rate of burning compared to untreated products were obtained.

Example IV Samples of medium weight, soft crepe paper were dipped into a 10% solution of ammonium sulfamate, pressed to remove excess solution, and dried at 75-100 C. The paper thus treated contained about 20-25% by weight of ammonium sulfamate but showed no increased harshness or stiffness. When the treated paper was brought into contact with a flame, it was only charred at the point of contact with the flame and showed no tendency to propagate a flame or to burn when the igniting flame was removed. Untreated paper readily burned completely when ignited.

Similar samples of the same paper treated as described above with other salts of sulfamic acid, such as the sodium, calcium, barium, zinc, aluminum, and ethylenediamine salts, likewise showed definite fire-retardant properties. However, ammonium sulfamate and ethylenediamine disulfamate were more effective as fire-retardants for the paper samples, on an equal weight basis, than the other salts mentioned.

Other grades of paper including a soft, tissue paper, a hard, flnished paper, and heavy sheets of paper wall-board, were similarly treated and similar results were obtained.

Example V A sheet of gel regeneratd cellulose was passed through a 6% aqueous solution of ammonium sulfamate, the excess solution removed by rolls, and the sheet then dried on a series of drying rolls. (The expression sheet of gel regenerated cellulose, or regenerated cellulose sheeting in gel form, here has reference to a sheet of cellulose which has been regenerated in the manner well known in the art from a solution of cellulose xanthate (viscose), washed and purified, but not dried. Regenerated cellulose sheeting in gel form may likewise be obtained from solutions of other suitable cellulose derivatives, e. g., cuprammonium solutions.) The dried cellulose sheet thus prepared contained about 18% by weight of ammonium sulfamate. The sheet was soft, flexible, clearand transparent and showed no crystallization of ammonium sulfamate even under conditions of low temperature and/or low humidity. When brought into contact with a flame the sheet showed excellent flame-proof properties. Under no conditions could the sheet, or a bundle of thin strips cut from such sheets, be made to propagate a flame. The sheet was charred only at the point of contact with the flame showing little or no afterflow when the flame was removed.

Similar sheets prepared as described above but with addition of glycerol to the ammonium sulfamate bath, so that the final product coniained about 6% glycerol and 18% by weight ammonium sulfamate, were equally flame-resistant.

Sheets of gel regenerated cellulose which had been treated with 5% aqueous solutions of ordinary fire-retardants such as ammonium phosphate and ammonium sulfate and dried showed undesirable crystallization of such salts in the film so that the sheet beca'me opaque and had a very rough crystalline surface. Also, these sheets were considerably more brittle than untreated sheets or sheets containing ammonium sulfamate.

Example VI Regenerated cellulose sheeting in the gel form was immersed in a 10% solution of ethylenediamine disulfamate for one minute, removed, and dried on a frame for 10 minutes at 100 C. After cooling, the cellulose sheet was soft, flexible, clear and transparent and showed excellent fire-retardant properties.

Regenerated cellulose similarly impregnated with other salts of sulfamic acid such as the pyridine, trimethylamine, zinc, aluminum, sodium and calcium salts, showed either a low tendency to burn or a retarded rate of burning, compared with plain untreated regenerated cellulose sheet. Such products showed either no crystallization or only slight crystallization of sulfamate within the transparent film under ordinary atmospheric conditions. Regenerated cellulose was similarly impregnated with unneutralized sulfamic acid and the product likewise showed definite fire-retardant properties compared to the untreated product.

As has been stated above, sulfamates have a softening as well as a fire-retarding action on regenerated cellulose as is illustrated by the results given in the following table.

The samples used in the above tests (except the control) were prepared by immersing the regenerated cellulose sheeting in 4% aqueous solutions of the sulfamates for one minute, removing and drying them at 100 C. for 13 minutes and conditioning them at 25 C. and 50% relative humidity for 24 hours. The measurements were made on the standard Scott machine. The control was identical in source and. preparation with the other samples except that it contained no sulfamate. The higher elongation and lower tensile strength at break in the case of the samples containing sulfamates indicates the latter exert aplasticizing action. Similar eifects in the case of paper and textiles can be recognized by one skilled in the art.

Example VII Dry maple wood blocks of A inch thickness, 1 inches wide and 3 inches long were immersed in various aqueous solutions containing 5-15% by weight of ammonium sulfamate. After drying, the treated samples contained from about 5 to 20% by weight of ammonium sulfamate based upon the original weight. In every case an increased ignition temperature and a decreased rate of burning were observed compared to uh treated samples. The wood samples containin about 20% by weight of ammonium suliamate; showed practically no afterglow when the ignites ing flame was removed.

White pine blocks containing from abouts-to- 15% by weight or ammonium sulfamate based'on the original dry weight likewise showed definite ilre-retardant properties as compared with" untreated samples.

Example VIII A thin sheet of polyvinyl alcohol containing ammonium sulfamate was obtained by evapor'alt; ing, on a glass plate, a layer of solution com prising by weight of high viscosity polyvinyl alcohol, 4% ammonium sulfamate and'f i'ii yf water. The product showed excellent fiexibllitii? and strength and showed a. decreased rate" burning when compared with similar sheets taining no ammonium sulfamate.

Example 1x '1 Example X A commercial sample of glassine paper was 'ex -f tracted consecutively with alcohol, acetone and water to remove all of the soluble organic arm:

stituents in the paper. The samples. thus treat ed. were then immersed for about one minute-in a 10% aqueous solution of ammonium sulfamatel After passing the paper between tightly fitting rubber rollers to remove excess solution. the paper sheets were dried at -80 C. for 15 minu es? The paper sheets thus treated, had approximately"- the same degree of transparency as the origin untreated paper and showed no crystallization ammonium sulfamate even at low temperatu and low humidity. Moreover, the treated glass'in paper was considerably softer in handle and fa than the extracted paper containing no ammon I um sulfamate. when brought into contact with" a flame the glassine paper impregnated with... ammonium sulfamate was dlfilcult to ignite and; did not propagate a flame, while both the erg; tracted and untreated control samples ware easily. ignited and burned rapidly.

Example xr 1 A velvet fabric of woven silk with a rayon'f (regenerated cellulose) pile was brought into con tact with an 8% aqueous solution of ammonium. sulfamate in such manner thatonly the bf side of the fabric was moistened while the ray pile surface was not wetted. After drying, the weight of the treated fabric has increased about. 15% of its original weight owing to the 5mg. monium sulfamate which has been absorbed. llhe dry fabric showed no visible crystallization of ammonium sulfamate and showed no tendency; dust or crock (a common. result with ordina fire-retardants on pile fabrics). Moreover. the" 1abl'lc showed no increased harshness in handle.

or feel while the luster. gloss, and general appearanceiawasiimprovedifby the above treatmnti when :brought. into ontac was a dam e 5 would not propagate a flame;while tiie uin'treatetl fabric was? easily ignited and rapidly.

A coating omposition wa's prepared bysmixing lfl-ap'art'srofra 52%':-linseed oilvmodifiediipolyhydric alcoholspolybasic acidsresinti having. an acid mum-i bera'ofn4;.and. dissolved in'i-ilil i parts petroleum droc'arbon fractionfivBi Pa 1C., Mim -l0 parts 20f. finely-1 pulverized ammonium sulfaniate and iaudingnthereto about o. part oi' cobalt linoieateidrieri This composition was spread in acmmuayer over 'c'otton vbile cloth' which had been previously; i-iiame:prooieii by mpregnation" with 15 by-weight onammonium suirama After 'drying;=theproductha an art I tran lucent appearance t-"=was 'sistaiiit to wetunc by -wate'r and- 'stri propagate- 9.; flame- 1 wlth' "'a.-flalli;- 'ifhe amej iabric dated corresponding-amount f the-3am I sir'i p sitibn' butfcdht'ainin h mmonium smiamate pha e?! sulfa'matetr fir retardanti '"wouldpropagat"=a nsure slowly" I such as amines, only those in which the ratio of carbon atoms to nitrogen atoms is less than about 3:1 are effective, this probably being due to excessiveheat of combustion derived from the burning of large organic carbon residues, which tends to nullify the effect of the protective incombustible gases (ammonia and/or nitrogen) which are apparently formed. However, regardless of the accuracy of this theory, the above generalization is indicated as approximately correct from tests with a variety of sulfamates. Thus, ammonium sulfamate, which has no carbon and two nitrogens, is most effective. Monomethylamine sulfamate and ethylenediamine disulfamate, which have a carbon-nitrogen ratio of 1:2, are excellent fire-retardants though not quite so efiective as ammonium sulfamate. 'Irimethylamine sulfamate having a carbon-nitrogen ratio of 3:2 is only moderately effective as are the dimethylamine and ethylamine sulfamates, whose ratio is 1:1. Pyridine sulfamate, wherein the carbonnitrogen ratio is 5:2, is a relatively poor fire-retardant and anilin sulfamate, of ratio 3:1, while effective to some extent especially in higher con centration is less eflective than would ordinarily be desired for commercial use. The above statements are made of course on the basis of comparable quantities of sulfamate and it should be made clear that in the majority of cases ex cellent results may be obtained with the lesser eifective sulfamates if they are employed in sufllciently large amounts. In the case of amine salts of sulfamic acid, the cation is the substituted ammonium radical; for example the cation in methyl amine sulfamate is (CH3.NH:.H). The latter compound is also properly designated as monomethyl ammonium sulfamate of the formula CHaNHa-HSOs-NH2.

In the case of salts from sulfamic acid and inorganic bases (1. e., metallic salts), only those having a metallic content of less than about 52% by weight of the anhydrous salt have any detectable eifect. This may be due to the relatively lower amount of non-combustible gases capable of liberation by the very heavy metal sulfamate molecule, but, regardless of the explanation, the generalization appears, on the basis of tests I have carried out with several metallic sulfamates, to be a correct approximation. Thus aluminum suifamate of 8.6% metallic content, is 'a very good fire-retardant whereas anhydrous zinc sulfamate of metallic content 25.4% is only moderately effective on an equal weight basis though in large amounts it approaches the aluminum salt in effectiveness. At the lower end of the scale, lead sulfamate of metallic content 51.9% has only a slight fire-retarding action. The sodium, potassium, calcium, magnesium, cobalt, nickel, manganese, and cadmium salts all impart flame-resistance to a degree proportionate to the non-metallic content of the sulfamate. All these tests bear out the conclusion that the metallic content of the sulfamate should be less than 52% if the sulfamate is to have any detectable effect and less than about 26% if it is to have any very important effect. Conversely the non-metallic content (including sulfur) should be at least 48% and preferably at least 74%.

Many of the sulfamic acid salts, such as zinc sulfamate, readily absorb water of crystallization. The hydrated salts may be used if desired in the present invention.

Bulfamic acid itself may also be used as a fireretardant and its effectiveness is only slightly less than the ammonium salt. However, the use of sulfamic acid in many instances is not desirable because of its acidity and the corresponding deterioration effects which may result from such acidity. The salts of sulfamic acid are practically neutral and therefore more practical when an acid reaction is not desirable.

Salts of sulfamic acids in which a hydrogen atom of the NH: group is replaced by a hydrocarbon radical, such as ammonium salts of N- 'methyiand N-isobutylsulfamic acids, are effective as fire-retardants, as are salts of iminodisulfamic acid such as diammonium iminodisuli'onate (NH4SOaNI-ISOaNH4).

The compounds with which the present invention is concerned are all included by the comprehensive formula (R'-NH--SO;|)=R in which R'is preferably hydrogen but may be a hydrocarbon radical or the radical NH4BOa--. and R is a cation of valence x, which compound has less than three carbon atoms for each nitrogen and a non-metallic content of at least 48%.

In the practice of the present invention the sulfamic acid or salt thereof may be employed in conjunction with ordinary fire-retardants such as ammonium phosphates, ammonium sulfate, boric acid, borax, ammonium carbonate, and ammonium halides with results and advantages proportionate to the relative amount of sulfamic acid or sulfamate employed.

The concentration of impregnated fire-retardant which is necessary will vary with the effectiveness of the retardant, the degree of fire-retardance desired, and the relative combustibility of the material to which applied. In general,

'um sulfamate give less eflective'protection but in every case show a decreased rate of burning compared to untreated materials. Lead sulfamate is only slightly effective as a fire-retardant for regenerated cellulose film and when impregnated into paper or cotton cloth it has no appreciable ilre-retarding'influence. 0n the other hand, the zinc salt is definitely eflective with all these types of materials, and the aluminum salt is highly effective with all of them.

In the examples, the sulfamate is applied from aqueous solution. Fire-retarding effects may also be obtained when the sulfamate is applied by any method. For example, powdered crystals may be dusted upon a damp surface or surface treated with adhesive: the sulfamate may be applied from solution or suspension in an organic liquid; or in the case of a liquid the sulfamate may be incorporated by mixing or milling.

The sulfamates of the amines may be prepared by the reaction of sulfamic acid with the amine preferably in aqueous solution. Metallic salts may be prepared by the methods known in the art, e. g., reaction of a freshly precipitated, washed, hydroxide or carbonate of the metal with an aqueous solution of sulfamic acid.

An outstanding advantage of ammonium suifamate and related salts over the more commonly used prior art flame-proofing agents for textile fabrics is the fact that they do not cause the harshness which normally characterizes fabrics treated with the prior art materials and in many instances they have a softening effect of their own. As flame-proofing agents for regenerated cellulose film, ammonium sulfamate and related salts have an advantage over prior art materials in that, even when present in the film in amounts up to about 23%, they do not crystallize out on the surface of the film under ordinary atmospheric conditions (24 C. and 35% relative humidity) as is characteristic of prior art flameproofing materials. Under favorable conditions, the amount may be as high as 30% without crystallizing out. Furthermore, ammonium sulfamates not only render cellulose and its manufactures (film, thread, fabrics, caps, bands, sponges, etc.) flame-proof, but also impart to these materials a certain degree of softness. Hence the sulfamates may also be used, either alone or in conjunction with glycerol or other common softener, as combined softening and flame-proofing agents. In the case of rayon, the ,sulfamate may be included in the viscose spinning bath, or it may be applied to the rayon thread or fabric. In the case of cellulose film, the sulfamate may be added with good results to the viscose, to the undried sheet, or to the dried sheet before or after application of moistureproofing lacquers, such as those of Charch and Prindle (U. S. 1,737,187 and 1,826,696). The fact that the moistureproofing lacquer may contain highly inflammable substances does not seem to make any appreciable difference. The cellulose thread, fabric, or film which has been impregnated with the sulfamate may be stored for prolonged periods without deterioration by the sulfamates inasmuch as the latter are substantially neutral.

Sulfamic acid and its salts may also be employed as fire-retardants for other celluloslc materials, which term is intended to include cellulose derivatives as well as cellulose, and manufactures of both. Examples of such additional cellulosic materials are cellulose esters such as the nitrate, acetate, propionate, butyrate, and pathalate and cellulose ethers such as methyl, ethyl-, benzyl-, crotyl-, hydroxyethyland carboxymethylcelluloses. These cellulose derivatives may be undegraded or highly degraded, of any degree substitution, and of any degree of water-sensitivity. A particular illustration of the flameproofing of a cellulose derivative is the inclusion of ammonium sulfamate in cellulose nitrate compositions containing pigments and softeners which are to be applied to fabrics; alternatively the sulfamate may be applied to the already coated fabric.

Fabrics that have been treated with sulfamic acid and those of its salts with which this invention is concerned, and thus rendered fire resistant, may be subsequently rubberized and the rubber coating vulcanized 'under the usual conditions (about 2 to 3 hours at about 120 C.) without appreciable tendering of the fabric.

Sulfamic acid and those of its salts specified herein are effective as fire-retardants, so far as is known, for any non-volatile combustible organic material whatever. Cellulosic materials, with which the advantages of this invention are most apparent, have been discussed in detail. Other materials are proteins and their manufactures such as films and filaments from casein, gelatin, zein, giiadin, edestin and the like; natural and synthetic resins such as rosin, ester gum, alkyd resins, polymeric esters of acrylic and methacrylic acid, vinyl resins, ether resins, and films and plastics made therefrom; natural and synthetic oils and films therefrom, such as linseed oil, linoxyn, and divlnylacetylene polymer; rubber and synthetic rubbers; leather, silk, and wool; and any combustible substance whatever.

The above description and examples are intended to be illustrative only. Any modification of or variation therefrom which conforms to the spirit of the invention is intended to be included within the scope of the claims.

I claim:

l. A product comprisinga non-volatile organic combustible material and, in sufficient amount to act as a fire-retardant therefor, a compound of the formula (R'-'-NH--SO3)1R wherein R is hydrogen, a hydrocarbon radical or NA4SOa-, R. is a cation of valence a: and a: is a whole number, said compound having less than three carbon atoms for each nitrogen atom and having a nonmetallic content of at least 48%.

2. A product comprising a non-volatile organic combustible material and, in suificlent amount to act as a fireretardant therefor, a compound of the formula (NHzSOshR, R being a cation of valence x, which compound has a non-metallic content of at least 48% and less than'three carbon atoms for each nitrogen atom.

3. A product comprising a non-volatile organic combustible material and, in sumcient amount to act as a fire-retardant therefor, a salt of sulfamic acid having a non-metallic content of at least 48% and less than three carbon atoms for each nitrogen atom.

4. A product comprising a. non-volatile organic combustible material and, in sufficient amount to act as a fire-retardant therefor, a salt of sulfamic acid having a non-metallic content of at least 74% and less than three carbon atoms per nitro-. gen atom.

5. A product comprising a non-volatile organic combustible material and, in sufficient amount to act as a fire-retardant therefor, ammonium sulfamate.

6. A product according to claim 2 in which the combustible substance is a cellulosic material.

7. A product according to claim 3 in which the combustible substance is a cellulosic material.

8. A product according to claim 4 in which the combustible substance is a cellulosic material.

9. A product according to claim 5 in which the combustible substance is a. cellulosic material.

10. A product comprising a fibrous cellulosic material and, in sufiicient amount to act as a fireretardant therefor, a. salt of sulfamic acid having a non-metallic content of at least 48% and less than three carbon atoms for each nitrogen atom.

11. A product comprising a fibrous cellulosic material and, in sufiicient amount to act as a fireretardant therefor, a salt of sulfamic acid having a non-metallic content of at least 74% and less than three carbon atoms per nitrogen atom.

12. A product comprising a, fibrous cellulosic material and, in sufiicient amount to act as a fireretardant therefor, ammonium sulfamate.

13. A product comprising paper and, in sufficient amount to act as a fire-retardant therefor, a salt of sulfamic acid having a non-metallic content of at least 48% and less than three carbon atoms for each nitrogen atom.

14. A product comprising paper and, in sufllcient amount to act as a fire-retardant therefor, a salt of sulfamic acid having a non-metallic content of at least 74% and less than three carbon atoms per nitrogen atom.

15. A product comprising paper and, in suflicient amount to act as a fire-retardant therefor, ammonium sulfamate.

16. A product comprising wood and, in willcient amount to act as a fire-retardant therefor,

a salt of sulfamic acid having a non-metallic content of at least 48% and less than three carbon atoms for each nitrogen atom.

17. A product comprising wood and, in sun!- cient amount to act as a fire-retardant therefor, a salt-of sulfamic acid having a non-metallic content of zit least 74% and less than three carbon atoms per nitrogen atom.

18. A product comprising wood and, in suflicient amount to act as a fire-retardant therefor,

ammonium sulfamate.

19. A product comprising a cotton textile and,

MARTIN ELI CUPERY.

CERTIFICATE OF CORRECTION.

January 5, 1959 MARTIN ELI GUPERY. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, second column, line 11;, claim 1, for "NA SO read NH SO -q and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 16th day of May, A. D. 1959.

(Seal) Henry Van Arsdale Acting Commissioner of Patents. 

